1. Field of the Invention
This invention relates generally to apparatus and methods for treatment of wastewater and, more particularly, to apparatus and methods for aerobic and anaerobic treatment of wastewater in a single tank employing an inverted cone clarifier.
2. Prior Art
Relatively small, self-contained wastewater treatment systems are being employed throughout the country for treatment of wastewater from domestic sources, particularly single family dwellings located in areas which are not served by larger municipal collection and treatment systems. Many different designs for those systems are used.
One treatment system design employs a single cylindrical tank having an inverted cone clarifier positioned within the tank with four radially spaced air pipes delivering air into the tank outside of the clarifier, as illustrated in U.S. Pat. No. 4,650,577, invented by Mr. Bradley L. Hansel (hereafter referred to as the "inverted cone system"). The geometry of the inverted cone system has proven to be a cost efficient and effective way to treat domestic sewage. It and other similar systems have focused, not on mixing, but on raising the dissolved oxygen content of the wastewater within the tank, thus providing additional support for the aerobic bacteria which feed on the wastewater. An example of such an attempt can be seen in U.S. Pat. No. 5,221,470, invented by Mr. Jerry L. McKinney. In this system, two air pipes deliver air to the lower portion of the tank and terminate at diffusers, which produce fine bubbles to maximize oxygen transfer to the wastewater.
The prior art does not contain an inverted cone treatment system that is capable of providing aerobic and anaerobic treatment and of removing nitrogen in a single apparatus. Therefore, what is desired is a system that retains the basic geometry of the inverted cone system and is capable of providing aerobic and anaerobic treatment of wastewater as well as denitrifying the same.